Caption: Bumble bee (Bombus sp.) pollinating a flower. As the bee sucks nectar from the flower, it rubs against the stamens - picking up grains of pollen. Each pollen grain contains a male gamete which, when deposited on another plant of the same species, can fertilise an ovule and produce seeds. Bumble bees are sociable but have relatively few members in their colonies; often fewer than 50 individuals. They feed on nectar and gather pollen for their young. They are one of the few insects able to regulate their temperature, using both solar radiation and internal cooling and warming mechanisms.